Dislocations of the acromial end of the clavicle
Injuries to the acromioclavicular joint occur due to direct or indirect trauma. The key task for the physician is to distinguish between subluxation and complete dislocation, as treatment tactics depend crucially on this.
In subluxation, exclusively the acromioclavicular ligament is affected. The patient experiences moderate pain, and local edema is mild. During scapular movements, the clavicle moves synchronously.
In complete dislocation, two ligaments are ruptured simultaneously: the acromioclavicular and coracoclavicular ligaments. Pain is sharp, and the acromioclavicular test is strongly positive. Synchrony of movement with the scapula is lost.
For an accurate diagnosis, comparative radiography of both clavicles is required. Radiological criteria for complete dislocation:
- Clavicular vertical displacement exceeds half of its thickness.
- The distance from the clavicle to the coracoid process increases by 5 mm or more (this is direct evidence of coracoclavicular ligament rupture).
Dislocations of the sternal end of the clavicle
Ruptures of the sternoclavicular joint are significantly less common, but require increased attention. The joint is stabilized by the sternoclavicular and costoclavicular ligaments. The injury is usually indirect (e.g., from pressure on the shoulder joints in the frontal plane).
Two main types of displacement are distinguished:
- Anterior (antesternal) dislocation: the clavicle displaces anteriorly and superiorly. Visual bone protrusion is observed, and palpation is painful.
- Posterior (retrosternal) dislocation: the clavicle displaces posteriorly and superiorly, forming a depression in the joint area.
Posterior dislocations are extremely dangerous. In approximately 25% of cases, they are accompanied by severe complications due to the pressure of the displaced bone on chest structures. Pneumothorax, compression or rupture of the subclavian artery and vein, as well as injury to the superior vena cava are possible.
Basic diagnostics include radiography (the shadow of the sternal end is shifted superiorly and medially), however, the optimal method for spatial assessment of the injury is computed tomography (CT).
Principles of treatment and reduction
At the pre-hospital stage, analgesia with painkillers and fixation of the arm with a sling are sufficient.
Closed reduction Reduction of a fresh dislocation is usually straightforward. Under anesthesia (local for acromial and anterior sternal, general for posterior sternal), the limb is pulled while simultaneously applying pressure to the displaced end of the clavicle. The main challenge is to maintain the bone in the correct anatomical position after the manipulation.
Conservative treatment Is justified only for subluxations. Bandages that create vertical pressure on the clavicle are used (e.g., plaster thoracobrachial bandage with a screw pelotte according to Shimbaretsky). Duration of immobilization is 4–6 weeks. In modern practice, this method is rarely used due to numerous drawbacks: high risk of pressure ulcers, frequent displacement recurrences, restriction of chest excursion, and extreme patient discomfort.
Surgical treatment This is the method of choice for complete dislocations.
- In incomplete dislocation (subluxation): percutaneous transarticular pin fixation followed by wearing a soft Desault bandage can be used.
- In complete dislocation: a mandatory condition is the restoration of the ruptured coracoclavicular ligament (using synthetic material or autogenous tissue). Additionally, the joint is fixed with pins.
In modern traumatology, rigid fixation methods that do not require subsequent plaster casting are actively used: implantation of «shape memory» structures made of nickel-titanium or fixation with a special hook plate.
Ability to work after treatment of a clavicle dislocation is fully restored on average in 7–8 weeks.
Briefly: answers to topical questions
What is the clinical «piano key» sign in a dislocation of the acromial end of the clavicle?
The clinical «piano key» sign consists of the reduction (depression) of the upwardly displaced distal end of the clavicle when pressure is applied to it. When the pressure is released, the clavicle shifts upward again, returning to its initial pathological position. To elicit the sign, the patient is supported under the elbow and pressure is applied to the prominent acromial end of the clavicle. In chronic dislocations, the sign may become incomplete, where the clavicle does not depress fully upon pressure.
What are the grades of acromioclavicular joint injury according to the Rockwood classification?
According to the Rockwood classification, six types of acromioclavicular joint injury are distinguished.
- Type 1 — partial tear or sprain of the acromioclavicular ligament with an intact coracoclavicular ligament.
- Type 2 — tear of the acromioclavicular ligament and partial tear or sprain of the coracoclavicular ligament.
- Types 3–6 — characterized by rupture of both the acromioclavicular and coracoclavicular ligaments.
- Type 5 — the distance between the clavicle and the coracoid process is 200–400% of normal.
- Type 6 — subacromial or subcoracoid displacement of the clavicle.
Exact descriptions of types 3 and 4 are omitted in the sources.
What types of dislocations of the sternal end of the clavicle exist depending on the direction of displacement?
Depending on the direction of displacement of the proximal end, two main types of dislocations of the sternal end of the clavicle are distinguished.
- Anterior dislocation (presternal, antesternal) — the sternal end of the clavicle is displaced anteriorly and superiorly, which is clinically manifested by its anterior protrusion.
- Posterior dislocation (retrosternal) — the clavicle is displaced posteriorly and superiorly, accompanied by a depression of the sternal end.
Posterior dislocations are less common, but in a quarter of cases lead to severe complications due to dorsal displacement (pneumothorax, vascular occlusion or rupture).
What radiography technique is used for the differential diagnosis of subluxation and complete clavicle dislocation in doubtful cases?
For the differential diagnosis of subluxation and complete clavicle dislocation, functional radiography with static load is used. The technique involves performing comparative radiography of both shoulder girdles (acromioclavicular joints) with the patient standing. In this procedure, loads weighing from 2 to 5 kg are attached to both upper limbs. This allows for the assessment of vertical joint stability and provides a clearer picture when standard imaging results are inconclusive.
The «piano key» sign — you press on the protruding end of the clavicle, it drops back into place; you release it — it «jumps» back up like a piano key.
Class and exam questions
How to distinguish a complete acromial dislocation from a subluxation on a radiograph?
In complete dislocation, the clavicle displacement exceeds half its thickness, and the distance to the coracoid process is increased by 5 mm or more compared to the healthy side.
Why is conservative treatment of superior acromial dislocations rarely used nowadays?
Due to the high risk of pressure sores from rigid pressure bandages, patient discomfort, respiratory restriction, and frequent recurrence of dislocation due to fixation loosening.
What are the dangers of a posterior dislocation of the sternal end of the clavicle?
The posteriorly displaced clavicle can cause a pneumothorax, compress or rupture subclavian vessels, and damage the superior vena cava.
What else to study on this topic
- Technique of percutaneous transarticular pin fixation
- Types of materials for coracoclavicular ligamentoplasty
- Biomechanics of «shape memory» structures (nickel-titanium)
- Surgical technique of transosseous suture in sternal end dislocation
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